1. Field of the Invention
The invention relates to phased array antenna systems with signal processing, such as used in radar or direction finding equipments.
2. Description of the Prior Art
In prior art radar systems a major problem concerns removal of signals from unwanted directions of arrival, while leaving signals from desired directions largely unaffected for subsequent signal processing. This problem is not confined to phased array systems and also occurs with mechanically steered dish antennas. For example, British Pat. No. 1,508,952 (and the corresponding U.S. Pat. No. 4,060,807) describe the problem in detail for a low-angle tracking radar using a parabolic dish antenna and discloses a form of what may be termed "spatial filtering" to overcome the problem.
Notwithstanding the prior art approaches to the problem, a substantial need remains for more effective angular (spatial) filtering. The manner in which the invention addresses the problem and, provides a novel solution, will be understood at this description proceeds.